Sleep apnea syndrome, a medical condition characterized by the periodic cessation of breathing during sleep, has been classically defined as embracing two types. Central sleep apnea syndrome involves a repeated loss of respiratory effort during sleep, and obstructive sleep apnea syndrome involves a repeated number of apneic episodes during sleep caused by an obstruction of the upper airway.
Treatment for central sleep apnea syndrome has included the use of various medications, such as protriptyline, medroxyprogesterone, acetazolamide, theophylline and nicotine, and the avoidance of central nervous system depressants such as sedatives and alcohol. Such treatment has occasionally been of some benefit but has rarely been completely effective.
Electrical stimulation has also been used to regulate and control the diaphragm of a patient. This procedure, called diaphragmatic pacing, is disclosed in Direct Diaphragm Stimulation, by J. Mugica et el., PACE, Vol. 10, January-February, 1987, Part II; Preliminary Test of a Muscular Diaphragm Pacing System on Human Patients, by J. Mugica et al., from Neurostimulation: An Overview, 1983, pages 263-279: and Electrical Activation of Respiration, by Nochomovitez, IEEE Eng. in Medicine and Biology, June 1983. Many patients suffering from central sleep apnea syndrome also have some degree of obstructive sleep apnea syndrome, however; and this condition worsens when inspiratory force is augmented by a pacer. Additionally, ventilation induced by activation of the diaphragm tends to collapse the upper airway of the patient upon inspiration and to draw the patient's tongue anteriorly downward, obstructing the patient's throat.
Treatment for obstructive sleep apnea syndrome has included a surgical procedure to correct severe retrognathia and other surgical procedures such as uvulopalatopharyngoplasties and tonsillectomies. Such procedures have met with some success but have often been unacceptable to patients.
Weight reduction and the use during sleeping hours of various devices, such as airways and tongue and jaw positioners, have been partially effective; but these measures are inconvenient, cumbersome and uncomfortable, which makes their continued use for long periods unlikely.
The only completely effective procedure for treating obstructive sleep apnea is tracheostomy, but considerable morbidity and aesthetically based rejection attends such a procedure.
It has been demonstrated that upper airway muscles that maintain patency lose tone during obstructive apneic episodes. A description of this may be found in The Human Tongue During Sleep: Electromyographic Activity of the Genioglossus Muscle, by Sauerland and Harper, Experimental Neurology, 1976, 51, 160-170.
It has also been demonstrated that submental electrical stimulation can reverse upper airway obstruction, presumably by contracting the genioglossus muscle, which produces an anterior displacement of the base of the tongue. A description of this may be found in Effects of Submental Electrical Stimulation During Sleep on Upper Airway Patency in Patients with Obstructive Sleep Apnea, by Miki et al., Am Review of Resp Diseases, 1989, 140, 1285-1289. Other studies have suggested that submental electrical stimulation is not effective in many patients because electrical current must be passed through skin, subcutaneous tissue and genioglossus muscle. The amount of current required causes pain in many patients. It is possible to more effectively stimulate the genioglossus muscle by using electrodes implanted subcutaneously, but this procedure exposes patients to the risk of infection, pain and complications such as hypoglossal nerve and genioglossus muscle damage. There are also risks associated with general anesthesia.
While each of the procedures described functions with a certain degree of efficiency, none disclose the advantages provided by the electrical sublingual stimulation device of the present invention as is hereinafter more fully described.